The present application claims priority under 35 U.S.C. xc2xa7119 of German Patent Application No. 199 02 139.2, filed on Jan. 20, 1999, the disclosure of which is expressly incorporated by reference herein in its entirety.
The invention relates to a press arrangement for treating a fibrous material web, in particular a paper or cardboard web. A process utilizing this arrangement is also disclosed.
The invention provides a press arrangement of the type mentioned above that, with the most compact possible design and lowest possible manufacturing costs, particularly guarantees a dewatering that is as volume-saving as possible.
The invention thus provides at least two press gaps elongated in the web travel direction and positioned in succession, of which at least the first is double felted, and by forming the first elongated press gap between a shoe press unit and a press suction roll that is simultaneously provided as pick-up roll, which is looped around by a felt transferring the fibrous material web from a screen belt, by which felt the fibrous material web is guided to the first elongated press gap.
In one embodiment of the press arrangement according to the invention, the shoe press unit is formed by a shoe press roll that is positioned below and is common to both elongated press gaps, to which, in addition to the press suction roll, an additional mating roll that is positioned above is assigned.
Such a press arrangement, which includes two press gaps elongated in the web travel direction, can be manufactured in a cost-effective manner. An advantage of this arrangement is that no mutual line force influence occurs, so there is no cambering of the rolls. Additionally, volume-saving dewatering is guaranteed. Moreover, a flat through-gradient results, which means that a slower flow speed occurs in the two press gaps in the Z direction. Overall, optimum nip or gap dewatering is achieved. Since the web is removed from the screen by a suction roll that is simultaneously provided as a press roll, an extremely compact design is achieved overall. In particular, the two presses can be constructed without levers, which means that respective pressing, in particular by a respective hydraulic press shoe, occurs, which achieves a closed power flow within the seating.
The shoe press roll is preferably provided with a position-stable press casing guide, which always guarantees optimum web and/or felt guidance, independent of the respective operating conditions.
In a further advantageous alternative embodiment, the two elongated press gaps are formed by two separate shoe presses. In that regard, the two shoe presses preferably each include a shoe press roll, and the two elongated press gaps are then formed by the respective shoe press roll and the press suction roll simultaneously provided as pick-up roll or another mating roll.
The fibrous material web can be guided between the two elongated press gaps, preferably together with a felt, around a deflection roll that is preferably constructed as a suction roll.
It is useful for a felt to be guided through both elongated press gaps.
In a useful and practical embodiment of the press arrangement according to the invention, both press gaps that are elongated in the web travel direction are double felted. This provides a slight two-sidedness. As a result, no press roll ductors are necessary in the area of the second mating roll. Additionally, completely closed web guidance from the screen up to the dry section is possible. Advantageously, a maximum total of three felts is provided.
In an additional advantageous embodiment of the press arrangement according to the invention, the second elongated press gap viewed in the web travel direction is single felted. In that case, two felts are sufficient, to the extent that one of those felts is simultaneously guided through both press gaps.
Advantageously, at least one portion of the two press rolls forming the press gaps elongated in the web travel direction respectively has an open, in particular blind bored and/or grooved, press surface.
If both of the press gaps elongated in the web travel direction are double felted, each press roll can possess an open press surface.
If the second elongated press gap is single felted, the rear mating roll that forms this second press gap with a shoe press unit suitably has a press surface that is at least substantially closed. Such a smooth mating roll is appropriate for certain products, such as liners with white covering (xe2x80x9cwhite topxe2x80x9d).
In a preferred embodiment, dewatering of at least one elongated press gap occurs at least partially by spinning off water into at least one channel or the like.
It is also advantageous when at least one mating roll and/or the press suction roll is formed by a hollow roll supported on the inside.
The invention provides for a press arrangement for treating a web, including a press shoe unit, a press suction roll, at least one first press nip elongated in a web travel direction, the first press nip being formed between the shoe press unit and the press suction roll, the press suction roll being arranged as a web pick-up roll, at least one second press nip elongated in the web travel direction and positioned downstream of the first press nip relative to the web travel direction, at least first and second felts being arranged to be guided through the at least one first press nip, the first felt being arranged to loop around the press suction roll to pick-up the web from a screen belt whereby the web is transferred from the screen belt to the first felt, wherein the web is guided to the first press nip by the first felt and the web is guided through the first press nip between the first and second felts. The web may be a fibrous material web. The fibrous material web may be one of a paper and cardboard web. The shoe press unit may include a shoe press roll which is common to the first and second press nips. The second nip may include an additional mating roll and the shoe press roll. The additional mating roll may be arranged above the shoe press roll. The shoe press roll may include a position-stable shoe press roll. The web may be guided through the first press nip using no belts other than first and second felts and wherein the web is guided through the second press nip using only the second felt. The shoe press unit may include first and second shoe press rolls.
The arrangement may also include the first press nip being formed between the first shoe press roll and the press suction roll, and the second press nip being formed between the second shoe press roll and an additional mating roll. A central axis of the additional mating roll may be arranged above a central axis of the second shoe press roll relative to a horizontal plane. The central axis of the press suction roll may be arranged above a central axis of the first shoe press roll relative to a horizontal plane. The central axis of the second shoe press roll may be arranged above a central axis of the additional mating roll. The arrangement may further include a deflection roll wherein the web is guided through the first press nip, around the deflection roll, and through the second press nip. The first felt, the web, and the second felt may all be guided around the deflection roll. The deflection roll may be a suction roll. The first felt, the web, and the second felt may pass through the first press nip, and wherein the web and the second felt may pass through the second press nip.
The arrangement may include a third felt arranged to be guided with the web and second felt through the second press nip. The web may be guided through first and second press nips using no belts other than first, second, and third felt belts. The arrangement may have an entirely closed web guidance system. The second press nip may be single felted. The web may be guided through the first press nip using no belts other than first and second felts and wherein the web is guided through the second press nip using only the second felt. At least one of the shoe press unit, the press suction roll, and an additional mating roll may include a press surface having at least one of blind-bores and grooves. The first and second press nips may each be double felted. Each of the shoe press unit, the press suction roll, and the additional mating roll may have press surfaces having at least one of blind-bores and grooves. The second press nip may be single felted and include the additional mating roll and the shoe press unit. The additional mating roll may have a press surface which is substantially closed.
The arrangement may provide for a deflection roll wherein the web is guided through the second press gap in free tension from the additional mating roll to a deflection roll. A drying section may include at least one dry cylinder wherein the web is guided to the at least one dry cylinder from the deflection roll. The at least one channel may be located adjacent one of the first and second press nips, wherein the at least one channel collects water that is spun-off from the web after the web passed through one of the first and second press nips. The press suction roll may be a hollow deflection compensation roll. The second press nip may be formed between an additional mating roll and the shoe press unit wherein the additional mating roll comprises a hollow deflection compensation roll.
Moreover, the arrangement may include a deflection roll wherein the web is guided through the second press nip, to the deflection roll, and then to a dry cylinder. The deflection roll may be a suction roll. The a dry screen wherein the web is transferred from the second felt to the dry screen after leaving the second press nip and wherein the web and the dry screen loop around the deflection roll.
According to another aspect of the invention, there is provided a press arrangement for treating a web, which includes a press shoe unit, a web pick-up roll, a first press nip elongated in a web travel direction, the first press nip being formed between the shoe press unit and the web pick-up roll, a second press nip elongated in the web travel direction and positioned downstream the first press nip, a center suction roll disposed between the first and second press nips, a wire belt for delivering the web the web pick-up roll, a first felt for receiving the web from the wire belt and for guiding the web to the first press nip, a second felt which travels through the first press nip with the web and the first felt, an additional mating roll positioned to form the second press nip with the shoe press unit, a deflection roll, and a dryer cylinder wherein the web is guided through the first press nip with the first and second felts, around the center suction roll and through the second press nip with the second felt, and to the deflection roll, and wherein the web is transferred to a dryer screen before being guided to the dry cylinder. A third felt may be included which is guided through the second press nip with the web and second felt. The web may be transferred from the second felt to the dryer screen after the third felt disengages from the web. A web separation device may also be included which uses suction to assist the disengagement of the third felt from the web and second felt. The shoe press unit may further include a position stable shoe press roll. The position stable shoe press roll may further include an inside carrier for supporting at least two rows of moveable support elements, a first press shoe associated with the first press nip, a second press shoe associated with the second press nip, and a control device for controlling the movement of the support elements wherein the moveable support elements move the first and second press shoes when activated by the control device. The control device may utilize a differential pressure valve. A flexible press casing which is rotatable may be provided and a external hollow carrier may be included which is disposed between the inside carrier and the flexible press casing, wherein at least one press shoe is disposed between the press casing and the external hollow carrier. The shoe press unit may further include first and second shoe press rolls.
The arrangement may provide that the first press nip is formed between the first shoe press roll and the pick-up roll and the second press nip is formed between the second shoe press roll and an additional mating roll. The additional mating roll may have a surface having at least one of blind-bores and grooves. Alternatively, the additional mating roll may have a surface which is substantially closed. Each of the shoe press unit, the press suction roll, and the additional mating roll may include a surface having at least one of blind-bores and grooves. At least one water collection channel may be positioned on one side of the web and at least another water collection channel positioned on the other side of the web.
According to another aspect of the invention, there is provided a method for treating a web in an arrangement that includes first and second felts, a web belt, a web pick-up roll, a shoe press unit, a center suction roll, an additional mating roll, a dryer screen, and a dryer cylinder, in which the method includes guiding the web and the first felt to the web pick-up roll, the web being supported on the web belt, engaging the web with the second felt, feeding the web, the first felt, and the second felt through a first press nip which is elongated in a web travel direction, the first press nip being formed by the shoe press unit and the web pick-up roll, disengaging the first felt from the web, wrapping the web and the second felt around a portion of the center suction roll disposed between the first and second press nips, feeding the web and the second felt through a second press nip which is elongated in the web travel direction, the second press nip being formed by the shoe press unit and the additional mating roll, disengaging the second felt from the web, and transferring the web to the dryer screen for delivering the web to the dryer cylinder.
The method may include engaging the web with a third felt, feeding the web, second felt, and third felt through the second press nip, and disengaging the third felt from the web before the web is transferred to the dry screen. The method may also include feeding the web to a deflection roll after disengaging the second felt. The web may be engaged with the dry screen in the vicinity of the deflection roll. The method may provide for regulating the compression forces generated by each of the first and second press nips independently using a control device which activates moveable press shoes in the shoe press unit. The water may be caught that is pressed out of the web using at least one channel disposed adjacent one of the first and second press nips.
The invention may also provide for a method for treating a web in an arrangement that includes first and second felts, a web belt, a web pick-up roll, first and second shoe press rolls, a center suction roll, an additional mating roll, a dryer screen, and a dryer cylinder, in which the method includes guiding the web and the first felt to the web pick-up roll, the web being supported on the web belt, engaging the web with the second felt, feeding the web, the first felt, and the second felt through a first press nip which is elongated in a web travel direction, the first press nip being formed by the first shoe press roll and the web pick-up roll, disengaging the first felt from the web, wrapping the web and the second felt around a portion of the center suction roll disposed between the first and second press nips, feeding the web and the second felt through a second press nip which is elongated in the web travel direction, the second press nip being formed by the second shoe press roll and the additional mating roll, disengaging the second felt from the web, and transferring the web to the dryer screen for delivering the web to the dryer cylinder.
The method may provide for engaging the web with a third felt, feeding the web, second felt, and third felt through the second press nip, and disengaging the third felt from the web before the web is transferred to the dry screen. The method may provide for feeding the web to a deflection roll after disengaging the second felt. The method may include engaging the web with the dry screen in the vicinity of the deflection roll. The method may also include regulating the compression forces generated by each of the first and second press nips independently using a control device which activates moveable press shoes in the first and second shoe press rolls. The method may further provide for catching water that is pressed out of the web using at least one channel disposed adjacent one of the first and second press nips.
Other exemplary embodiments and advantages of the present invention may be ascertained by reviewing the present disclosure and the accompanying drawing.